Add executor runtime lease reclamation

[Jesse McGinnis (brayzn)]

Summary

• add a durable actor runtime lease with token/generation fencing and heartbeat renewal
• reclaim expired executor-owned actors natively before releasing their workers
• preserve the router's read-only ResumeActor fast path and use an explicit executor lease claim
• keep golden actor reconciliation lease-aware and preserve durable snapshots on crash

Recovery contract

The executor renews every 30 seconds. A 120-second lease expires without heartbeats; the ate-api reaper claims the expired row, terminates the live workload, releases the worker, marks the actor CRASHED, and removes the lease. A running command is not resumed after executor death; its durable workspace snapshot remains the recovery input.

Validation

• go test ./cmd/ateapi
• go test -count=1 ./cmd/ateapi/internal/controlapi ./cmd/ateapi/internal/store/atepg ./cmd/atenet/internal/router/ingress
• go test ./... (all relevant packages pass; existing non-TTY color tests fail in internal/e2e)

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